Q. I know that you use “to” and not an en dash with “from”: “from 2012 to 2016 (not from 2012–16).” But what about with “for”? Should it be “for 25 to 30 minutes” or “for 25–30 minutes”?
A. An en dash is allowed in number ranges preceded by “for”: “for 25–30 minutes.” The same goes for “in”: “in 25–30 minutes.” Try this test: if the expression would still make sense with only half the range, then an en dash would be correct (though it is always permissible to use “to” instead). “We stood there for 25 minutes” and “we completed the survey in 25 minutes” are both unambiguous. On the other hand, “we lived there from 2012,” though it is sometimes encountered in speech, is incomplete (from 2012 to when?). The preposition “between”—which pairs with “and” rather than “to”—fails the test even more conclusively (try it).